Photo-engraving



April 13 1926. 1,580,897

FL E.I\HE$ I PHOTO ENGRAVING I Filed May 17, 1924 Patented Apr. 13, 1926.

UNITED STATES PATENT OFFICE.

HERBERT E. IVES, OF MONTCLAIR, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

PHOTO-ENGRAVING.

Application filed May 17,

To all whom it may concern.-

Be it known that I, HERBERT E. IvEs, a citizen of the United States of America, re' siding at Montclair, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Photo- Engraving, of which the following is a full, clear, concisefand exact descrlption.

This invention relates to photo-engravings, and more particularly to a method and means for producing photoengravings from line pictures.

Experiments have proved that the more satisfactory and practical method of transmitting pictures electrically resides in the use of mechanism whereby the elemental tone values of the picture are transmitted as modulations of a voice frequency carrier wave, which are received at a distant station where mechanism is located for reproduclng the picture in the form of lines of uniform density and varying width. This form of picture, without modification, is not wholly satisfactory for use with photo-engraving 25 processes, in which a zinc or copper plate is adapted to be used in the stereotype copying process, owing to the lack of defin1t 1on in the light areas. These areas, when printed on news print paper, instead of being a pronounced white, have actually appeared a grayish white, so that the contrast between the lightest and darkest portion of the picture is not sufficiently marked to give a pleasing picture. It is therefore the object of the present invention to overcome the difliculties heretofore encountered, by producing from a line picture a picture composed of dots which, experience has proved, lends itself more readily to the making of photo-engravings such as are particularly suitable for newspaper work.

In accordance with the above object, the present invention contemplates the provision of means whereby a line picture may be reproduced in the form of linearly arranged dots, which may be either parallel with the lines of the picture or, without the introduction of interference patterns, diagonal thereto. The latter arrangement is preferable as it increases the definition of the picture, which is so essential for newspaper reproductions. Specifically, the invention provides, in connection with a photo enlarging camera, mechanism whereby the lines of the 1924. Serial No. 713,938.

picture and the lines of dots of the cross-line screen are parallel. In cases in which the lines ofdots are at an angle of 45 to the lines of the picture, the cross-line screen has a spacing equal to 5 times the spacing ture would be 85. By the use of such an arrangement, a picture is produced which possesses definition and which is pleasing to the eye when reproduced in newspapers and the like.

The embodiments of the invention are illustrated in the accompanying drawings, in which Fig. 1 shows the arrangement of the crossline screen with the picture positioned at an angle of 45 from the vertical.

v Fig. 2 shows the picture in its vertical position.

Fig. 3 represents the lines of the picture.

Fig. 4 shows the alignment of the dots for the arrangement shown in Fig. 2.

Fig. 5 is an elevation of the mechanism used in the photographic process.

Fig. 6 is a sectional view taken along the broken line 66 of Fig. 5. a.

Fig, 7 illustrates the mechanism for offecting the rotation of the picture to bring the lines thereof parallel to the lines of dots formed by the cross-line screen.

A better understanding of the invention may be had from the following description when-taken in conjunction with the accompanying drawings, which illustrate the embodiments of the invention.

Referring now for the moment to Fig. 5 a photographic enlarging camera is arranged with supports 6 and 7 for the bellows 8 and the lens 9, which are arranged, as

shown in Fig. 6, to move in parallel tracks 19 arranged on opposite sides of the supportin frame 20, and which are capable of being Io device 10. As is sometimes the practice in photographic enlarging cameras, especially those used in connection with photo-engraving, it is equipped so as to permit of a change in magnification without alterin the focus. Many methods for accoinplis ing this feature are now inoirporated in such devices, and since the mehanism per se does cked in a set position by a locking,

not form a part of this invention, detailed description thereof is thought unnecessary. Located to the rear of the camera and in front of the ground glass 11 is a cross-line screen 12 having a periodicity of 60. Following the practice in photographic engraving, the cross-line screen is set at an angle of 45 and is capable of being moved to adjust the distance from the negative to give correct dots. This mechanism may consist of cams 13, Fig. 6 operated by a lever for effecting the movement of the cross-line screen- The picture 14 to be photographed or copied which has previously been transmitted 15 electrically by transmitting the elemental tone values of the picture as modulations of a voice frequency carrier wave for effecting the exposure of a film to reproduce the picture in the form of lines of uniform density and varyin width or varying density and varying wi th is held in position on a mounting frame 15 by means of spring clips 16, Fig. 7. A convenient and desirable method for efl'ecting the transmission of pictures electrically is shown in my copending application Serial No. 711,755, filed May 8,

1924. Arranged on the periphery of the mounting frame 15 are a number of small rack sectors 17, which have their teeth meshed with pinions 18. For rotating the mounting frame 15, a lever having a bifurcated portion engaging a pin secured in the mounting frame 15 is provided. By the arrangement of the pinions, the rotation is equalized as well as being uniform on all sides. It will, of course, be understood that the amount of rotation of the mounting frame is slight, probably not exceeding plus or minus 5.

In most cases, immediately after the exposed film has been developed and before it has had an opportunity to dry, it is desired to produce a dot picture directly from the transparency in the form of lines, in which case it would, of course, be necessary to have a light source 21 with a suitable reflector located back of the transparency. It is to be noted that the mechanism also lends itself for use in making dot pictures from prints,

for when such is desired, the position of the light source need only be changed for producing a reflected light.

In the production of dot pictures from line pictures, in which the dots are arranged parallel to the lines of the picture, the picture to be reproduced is positioned in the frame 15 so -that its lines approximately coincide with the lines of the cross-line screen 12. As previously stated, it is sometimes the practice in photo-engraving processes to mount the cross-line screen at an angle of 45. In order to eliminate interference bands or patterns, thereby providing a patternless picture, it is necessary to rotate the 5 mounting frame 15, and in consequence the picture 14, to a point such that these interference bands disappear, which will be effected when the lines of the picture are parallel with the lines of dots formed by the cross-line screen. After this operation the magnification should be changed Without altering the focus to a point such that the interference bands, which become larger and larger as a magnification of unity is approached, finally disappear. A more practlcal operation, however, would be to again change the magnification to a point such that the interference bands again appear and select the correct position by an estimation of the point mid-way between the appearance of the equally spaced bands. The sensitive plate, which is of a character suitable for half tone dot rendering, is then inserted in the camera, and the picture, as viewed through the cross-line screen photographed. The picture will thus be reproduced in the form of dots which are parallel to the lines of the picture.

' In order to produce a dot picture having a structure identical with that usually seen in half tone reproduction, it is proposed to photograph the picture through a cross-line screen, so that the dots formed thereby will lie diagonal to the direction of the lines of the copied picture. To produce this condition it is necessary that the cross-line screen shall having a spacing of its constituent lines /2 times the spacing of the picture lines. Under this condition the lines of the picture agree in periodicity with the lines of dots formed by the cross-line screen in the direction of 45 to the constituent lines of the cross-line screen. According to Fig. 4, with the line spaces equal to X, the screen spaces would be x /2; or vice versa.

This result may be produced by mounting the picture 14 in the mounting frame 15 so that the picture lines make an angle of 45 with the lines of the cross-line screen 12. By following the operations outlined with respect to the photographing of a line picture to reproduce the picture so that the lines of dots thereof are parallel to the lines of the picture, the picture will be copied in the form that the lines of dots are in a direction diagonal to the lines of the picture. With the ordinary transparency of 85 lines and a cross-line screen of 60 lines, the result previously outlined will be accomplished and the picture finally reproduced will be entirely satisfactory for newspaper reproduction.

Imagine a picture which has been transmitted electrically by transmitting the elemental tone values of the picture as modulations of a voice frequency carrier wave, which reproduces at the receiving station what is known as a line picture having a periodicity of 85 placed in the mounting frame 15. Upon viewing the image on the ground glass 11, it will be observed to be traversed by numerous rather broad black bands, and these bands will ordinarily lie at a slight angle with the lines of the picture. By adjusting the position of the mounting frame 15, which consists in retating the picture around the axis of the camera, the interference bands or patterns may be brought parallel with the lines of the picture. When this is accomplished the magnification is then changed to something other than unity, say 1l' without altering the focus. The change of the magnification causes the interference bands to become larger and larger as the magnification of unity is approached, and finally disappear. The magnification should then be changed in the reverse direction to a point where the bands reappear, and by choosing a position by estimating the point mid-way between the appearance of the equally spaced bands, the proper and correct arrangement of the dots will be effected. F 01- lowing this operation, the copied picture may be photographed. as is customary in connection with photo-engraving operation.

It is, of course, obvious that various modifications and adaptations may be made without departing from the spirit and scope of the present invention.

What is claimed is:

1. The method of producing dot pictures from line pictures which consists in moving the picture to be reproduced relative to a cross-line screen until interference patterns are eliminated, and photographing the lined picture.

2. The method of producing dot pictures from line pictures consisting in moving the picture to be reproduced so that the lines of the image formed in a focal plane are parallel with the lines of dots formed by a. cross-line screen and of equal spacing and exposing a negative by a suitable photographic procedure to yielddots of varying size.

' 3. The method of producing from line pictures, which consists in rotating a transparency of a line picture to eliminate interference patterns by bringing a the lines of an image of the picture formed in a focalplane arallel with the lines of dots of a cross- 'ne screen and of equal dot pictures spacing and photographing the picture image through the cross-line screen.

4:. The method of reproducing line pictures in the form of dot pictures, which consists in' producing relative movement between the picture to be reproduced and a cross-line screen to eliminate interference patterns, and photographing the picture as lines of dots.

5. The method of producing line pictures in the form of dot pictures which consists in forming an image of the picture to be copied of a magnification other than unity, producing relative angular movement between the picture and a cross-line screen to bring interference bands parallel with the lines of the picture, adjusting the magnification until the interference bands finally diappear, and photographing the cross-line picture.

6. The method of producing line pictures in the form of dot pictures which consists in placing the picture to be reproduced at an angle of substantially 45 to the lines of a cross-line screen, changing the relative angular position of the screen lines and the picture lines until the interference bands formed between the lines of the picture and ,the lines of dots of the cross-line screen are parallel, adjusting the magnification until the interference bands finally disappear, and photographing the thus arranged picture, which results in the alignment of the lines of dots in a direction diagonal to the 1 lines of the picture.-

7. In combination, a photo-enlarging camera, means for altering the magnification without changing the focus, a line picture which has been received electrically from a distant station, a cross-line screen having a spacing equal to the #2 times the spacing of the picture lines, means for effecting relative movement between the cross-line screen and the picture to bring the lines of the picture parallel with the lines of dots of HERBERT E. IVES. 

